PROJECT SUMMARY: Methodology Core This Core focuses on economic evaluation approaches, tools, and measures to support new and existing interdisciplinary research collaborations. Despite decades of research supporting a chronic disease approach to substance use disorder treatment and recovery, uptake and sustainment remain low. Some of the most important factors inhibiting adoption of evidence-based practices are concerns about the potential burden on staff and other resources, as well as overall budget impact. Changing current practices requires not only clinical evidence, but also consideration of additional costs and the reallocation of existing resources that will result from the changes. Economic analysis can directly address these issues by providing a detailed accounting of the costs to the provider of updating services, and more broadly inform ?real-world? resource allocation decisions by providing policymakers and payers with evidence on the net economic and health impact of new approaches and their fiscal viability over time. This requires considering both costs and consequences of a new intervention, often using a cost-effectiveness or cost-benefit analysis framework. The overall aim of CHERISH (Center for Health Economics of Treatment Interventions for Substance Use Disorder, HCV, and HIV) is to develop and disseminate economic evidence that informs substance use disorder policy and HCV and HIV care of people who use substances. In this renewal period we will expand our focus to outcome and implementation research that is conducted at the individual, system, and community levels with the following specific aims: 1) to guide researchers in the design, implementation, and interpretation of economic analyses of treatment for substance use disorder, and HCV and HIV among people who use substances, and 2) to develop and apply methods that support economic evaluations for substance use disorder, and HCV and HIV among people who use substances with a focus on intervention implementation and adaptive interventions. Through the CHERISH Consultation Service and Research Affiliates Program, we will contribute to the development of new grant proposals with explicit economic aims, and will continue to connect with and advise qualifying researchers nationally to ensure that planned economic analyses are methodologically sound and feasible. We will expand the CHERISH Research Affiliates program so it can serve as a nationally-representative virtual community for researchers engaged in substance use disorder treatment health economic research. Working with existing studies and integrating data from third-party datasets and administrative records, we will develop analytic frameworks and tools for evaluating individual and systems-level substance use disorder and related implementation interventions. We will also develop economic evaluation methods for adaptive interventions. In collaboration with the Population Data & Modeling Core, we will assist researchers in using external data to enhance interpretation of economic evaluation results.